<?php
/**
 * This module contains code for dealing with associations between
 * consumers and servers.
 *
 * PHP versions 4 and 5
 *
 * LICENSE: See the COPYING file included in this distribution.
 *
 * @package OpenID
 * @author JanRain, Inc. <openid@janrain.com>
 * @copyright 2005-2008 Janrain, Inc.
 * @license http://www.apache.org/licenses/LICENSE-2.0 Apache
 */

/**
 * @access private
 */
require_once 'Auth/OpenID/CryptUtil.php';

/**
 * @access private
 */
require_once 'Auth/OpenID/KVForm.php';

/**
 * @access private
 */
require_once 'Auth/OpenID/HMAC.php';

/**
 * This class represents an association between a server and a
 * consumer.  In general, users of this library will never see
 * instances of this object.  The only exception is if you implement a
 * custom {@link Auth_OpenID_OpenIDStore}.
 *
 * If you do implement such a store, it will need to store the values
 * of the handle, secret, issued, lifetime, and assoc_type instance
 * variables.
 *
 * @package OpenID
 */
class Auth_OpenID_Association {
  
  /**
   * This is a HMAC-SHA1 specific value.
   *
   * @access private
   */
  var $SIG_LENGTH = 20;
  
  /**
   * The ordering and name of keys as stored by serialize.
   *
   * @access private
   */
  var $assoc_keys = array('version', 'handle', 'secret', 'issued', 'lifetime', 'assoc_type');
  
  var $_macs = array('HMAC-SHA1' => 'Auth_OpenID_HMACSHA1', 'HMAC-SHA256' => 'Auth_OpenID_HMACSHA256');

  /**
   * This is an alternate constructor (factory method) used by the
   * OpenID consumer library to create associations.  OpenID store
   * implementations shouldn't use this constructor.
   *
   * @access private
   *
   * @param integer $expires_in This is the amount of time this
   * association is good for, measured in seconds since the
   * association was issued.
   *
   * @param string $handle This is the handle the server gave this
   * association.
   *
   * @param string secret This is the shared secret the server
   * generated for this association.
   *
   * @param assoc_type This is the type of association this
   * instance represents.  The only valid values of this field at
   * this time is 'HMAC-SHA1' and 'HMAC-SHA256', but new types may
   * be defined in the future.
   *
   * @return association An {@link Auth_OpenID_Association}
   * instance.
   */
  function fromExpiresIn($expires_in, $handle, $secret, $assoc_type) {
    $issued = time();
    $lifetime = $expires_in;
    return new Auth_OpenID_Association($handle, $secret, $issued, $lifetime, $assoc_type);
  }

  /**
   * This is the standard constructor for creating an association.
   * The library should create all of the necessary associations, so
   * this constructor is not part of the external API.
   *
   * @access private
   *
   * @param string $handle This is the handle the server gave this
   * association.
   *
   * @param string $secret This is the shared secret the server
   * generated for this association.
   *
   * @param integer $issued This is the time this association was
   * issued, in seconds since 00:00 GMT, January 1, 1970.  (ie, a
   * unix timestamp)
   *
   * @param integer $lifetime This is the amount of time this
   * association is good for, measured in seconds since the
   * association was issued.
   *
   * @param string $assoc_type This is the type of association this
   * instance represents.  The only valid values of this field at
   * this time is 'HMAC-SHA1' and 'HMAC-SHA256', but new types may
   * be defined in the future.
   */
  function Auth_OpenID_Association($handle, $secret, $issued, $lifetime, $assoc_type) {
    if (! in_array($assoc_type, Auth_OpenID_getSupportedAssociationTypes())) {
      $fmt = 'Unsupported association type (%s)';
      trigger_error(sprintf($fmt, $assoc_type), E_USER_ERROR);
    }
    
    $this->handle = $handle;
    $this->secret = $secret;
    $this->issued = $issued;
    $this->lifetime = $lifetime;
    $this->assoc_type = $assoc_type;
  }

  /**
   * This returns the number of seconds this association is still
   * valid for, or 0 if the association is no longer valid.
   *
   * @return integer $seconds The number of seconds this association
   * is still valid for, or 0 if the association is no longer valid.
   */
  function getExpiresIn($now = null) {
    if ($now == null) {
      $now = time();
    }
    
    return max(0, $this->issued + $this->lifetime - $now);
  }

  /**
   * This checks to see if two {@link Auth_OpenID_Association}
   * instances represent the same association.
   *
   * @return bool $result true if the two instances represent the
   * same association, false otherwise.
   */
  function equal($other) {
    return ((gettype($this) == gettype($other)) && ($this->handle == $other->handle) && ($this->secret == $other->secret) && ($this->issued == $other->issued) && ($this->lifetime == $other->lifetime) && ($this->assoc_type == $other->assoc_type));
  }

  /**
   * Convert an association to KV form.
   *
   * @return string $result String in KV form suitable for
   * deserialization by deserialize.
   */
  function serialize() {
    $data = array('version' => '2', 'handle' => $this->handle, 'secret' => base64_encode($this->secret), 
        'issued' => strval(intval($this->issued)), 
        'lifetime' => strval(intval($this->lifetime)), 'assoc_type' => $this->assoc_type);
    
    assert(array_keys($data) == $this->assoc_keys);
    
    return Auth_OpenID_KVForm::fromArray($data, $strict = true);
  }

  /**
   * Parse an association as stored by serialize().  This is the
   * inverse of serialize.
   *
   * @param string $assoc_s Association as serialized by serialize()
   * @return Auth_OpenID_Association $result instance of this class
   */
  function deserialize($class_name, $assoc_s) {
    $pairs = Auth_OpenID_KVForm::toArray($assoc_s, $strict = true);
    $keys = array();
    $values = array();
    foreach ($pairs as $key => $value) {
      if (is_array($value)) {
        list($key, $value) = $value;
      }
      $keys[] = $key;
      $values[] = $value;
    }
    
    $class_vars = get_class_vars($class_name);
    $class_assoc_keys = $class_vars['assoc_keys'];
    
    sort($keys);
    sort($class_assoc_keys);
    
    if ($keys != $class_assoc_keys) {
      trigger_error('Unexpected key values: ' . var_export($keys, true), E_USER_WARNING);
      return null;
    }
    
    $version = $pairs['version'];
    $handle = $pairs['handle'];
    $secret = $pairs['secret'];
    $issued = $pairs['issued'];
    $lifetime = $pairs['lifetime'];
    $assoc_type = $pairs['assoc_type'];
    
    if ($version != '2') {
      trigger_error('Unknown version: ' . $version, E_USER_WARNING);
      return null;
    }
    
    $issued = intval($issued);
    $lifetime = intval($lifetime);
    $secret = base64_decode($secret);
    
    return new $class_name($handle, $secret, $issued, $lifetime, $assoc_type);
  }

  /**
   * Generate a signature for a sequence of (key, value) pairs
   *
   * @access private
   * @param array $pairs The pairs to sign, in order.  This is an
   * array of two-tuples.
   * @return string $signature The binary signature of this sequence
   * of pairs
   */
  function sign($pairs) {
    $kv = Auth_OpenID_KVForm::fromArray($pairs);
    
    /* Invalid association types should be caught at constructor */
    $callback = $this->_macs[$this->assoc_type];
    
    return call_user_func_array($callback, array($this->secret, $kv));
  }

  /**
   * Generate a signature for some fields in a dictionary
   *
   * @access private
   * @param array $fields The fields to sign, in order; this is an
   * array of strings.
   * @param array $data Dictionary of values to sign (an array of
   * string => string pairs).
   * @return string $signature The signature, base64 encoded
   */
  function signMessage($message) {
    if ($message->hasKey(Auth_OpenID_OPENID_NS, 'sig') || $message->hasKey(Auth_OpenID_OPENID_NS, 'signed')) {
      // Already has a sig
      return null;
    }
    
    $extant_handle = $message->getArg(Auth_OpenID_OPENID_NS, 'assoc_handle');
    
    if ($extant_handle && ($extant_handle != $this->handle)) {
      // raise ValueError("Message has a different association handle")
      return null;
    }
    
    $signed_message = $message;
    $signed_message->setArg(Auth_OpenID_OPENID_NS, 'assoc_handle', $this->handle);
    
    $message_keys = array_keys($signed_message->toPostArgs());
    $signed_list = array();
    $signed_prefix = 'openid.';
    
    foreach ($message_keys as $k) {
      if (strpos($k, $signed_prefix) === 0) {
        $signed_list[] = substr($k, strlen($signed_prefix));
      }
    }
    
    $signed_list[] = 'signed';
    sort($signed_list);
    
    $signed_message->setArg(Auth_OpenID_OPENID_NS, 'signed', implode(',', $signed_list));
    $sig = $this->getMessageSignature($signed_message);
    $signed_message->setArg(Auth_OpenID_OPENID_NS, 'sig', $sig);
    return $signed_message;
  }

  /**
   * Given a {@link Auth_OpenID_Message}, return the key/value pairs
   * to be signed according to the signed list in the message.  If
   * the message lacks a signed list, return null.
   *
   * @access private
   */
  function _makePairs(&$message) {
    $signed = $message->getArg(Auth_OpenID_OPENID_NS, 'signed');
    if (! $signed || Auth_OpenID::isFailure($signed)) {
      // raise ValueError('Message has no signed list: %s' % (message,))
      return null;
    }
    
    $signed_list = explode(',', $signed);
    $pairs = array();
    $data = $message->toPostArgs();
    foreach ($signed_list as $field) {
      $pairs[] = array($field, 
          Auth_OpenID::arrayGet($data, 'openid.' . $field, ''));
    }
    return $pairs;
  }

  /**
   * Given an {@link Auth_OpenID_Message}, return the signature for
   * the signed list in the message.
   *
   * @access private
   */
  function getMessageSignature(&$message) {
    $pairs = $this->_makePairs($message);
    return base64_encode($this->sign($pairs));
  }

  /**
   * Confirm that the signature of these fields matches the
   * signature contained in the data.
   *
   * @access private
   */
  function checkMessageSignature(&$message) {
    $sig = $message->getArg(Auth_OpenID_OPENID_NS, 'sig');
    
    if (! $sig || Auth_OpenID::isFailure($sig)) {
      return false;
    }
    
    $calculated_sig = $this->getMessageSignature($message);
    return $calculated_sig == $sig;
  }
}

function Auth_OpenID_getSecretSize($assoc_type) {
  if ($assoc_type == 'HMAC-SHA1') {
    return 20;
  } else if ($assoc_type == 'HMAC-SHA256') {
    return 32;
  } else {
    return null;
  }
}

function Auth_OpenID_getAllAssociationTypes() {
  return array('HMAC-SHA1', 'HMAC-SHA256');
}

function Auth_OpenID_getSupportedAssociationTypes() {
  $a = array('HMAC-SHA1');
  
  if (Auth_OpenID_HMACSHA256_SUPPORTED) {
    $a[] = 'HMAC-SHA256';
  }
  
  return $a;
}

function Auth_OpenID_getSessionTypes($assoc_type) {
  $assoc_to_session = array('HMAC-SHA1' => array('DH-SHA1', 'no-encryption'));
  
  if (Auth_OpenID_HMACSHA256_SUPPORTED) {
    $assoc_to_session['HMAC-SHA256'] = array('DH-SHA256', 'no-encryption');
  }
  
  return Auth_OpenID::arrayGet($assoc_to_session, $assoc_type, array());
}

function Auth_OpenID_checkSessionType($assoc_type, $session_type) {
  if (! in_array($session_type, Auth_OpenID_getSessionTypes($assoc_type))) {
    return false;
  }
  
  return true;
}

function Auth_OpenID_getDefaultAssociationOrder() {
  $order = array();
  
  if (! Auth_OpenID_noMathSupport()) {
    $order[] = array('HMAC-SHA1', 'DH-SHA1');
    
    if (Auth_OpenID_HMACSHA256_SUPPORTED) {
      $order[] = array('HMAC-SHA256', 'DH-SHA256');
    }
  }
  
  $order[] = array('HMAC-SHA1', 'no-encryption');
  
  if (Auth_OpenID_HMACSHA256_SUPPORTED) {
    $order[] = array('HMAC-SHA256', 'no-encryption');
  }
  
  return $order;
}

function Auth_OpenID_getOnlyEncryptedOrder() {
  $result = array();
  
  foreach (Auth_OpenID_getDefaultAssociationOrder() as $pair) {
    list($assoc, $session) = $pair;
    
    if ($session != 'no-encryption') {
      if (Auth_OpenID_HMACSHA256_SUPPORTED && ($assoc == 'HMAC-SHA256')) {
        $result[] = $pair;
      } else if ($assoc != 'HMAC-SHA256') {
        $result[] = $pair;
      }
    }
  }
  
  return $result;
}

function &Auth_OpenID_getDefaultNegotiator() {
  $x = new Auth_OpenID_SessionNegotiator(Auth_OpenID_getDefaultAssociationOrder());
  return $x;
}

function &Auth_OpenID_getEncryptedNegotiator() {
  $x = new Auth_OpenID_SessionNegotiator(Auth_OpenID_getOnlyEncryptedOrder());
  return $x;
}

/**
 * A session negotiator controls the allowed and preferred association
 * types and association session types. Both the {@link
 * Auth_OpenID_Consumer} and {@link Auth_OpenID_Server} use
 * negotiators when creating associations.
 *
 * You can create and use negotiators if you:

 * - Do not want to do Diffie-Hellman key exchange because you use
 * transport-layer encryption (e.g. SSL)
 *
 * - Want to use only SHA-256 associations
 *
 * - Do not want to support plain-text associations over a non-secure
 * channel
 *
 * It is up to you to set a policy for what kinds of associations to
 * accept. By default, the library will make any kind of association
 * that is allowed in the OpenID 2.0 specification.
 *
 * Use of negotiators in the library
 * =================================
 *
 * When a consumer makes an association request, it calls {@link
 * getAllowedType} to get the preferred association type and
 * association session type.
 *
 * The server gets a request for a particular association/session type
 * and calls {@link isAllowed} to determine if it should create an
 * association. If it is supported, negotiation is complete. If it is
 * not, the server calls {@link getAllowedType} to get an allowed
 * association type to return to the consumer.
 *
 * If the consumer gets an error response indicating that the
 * requested association/session type is not supported by the server
 * that contains an assocation/session type to try, it calls {@link
 * isAllowed} to determine if it should try again with the given
 * combination of association/session type.
 *
 * @package OpenID
 */
class Auth_OpenID_SessionNegotiator {

  function Auth_OpenID_SessionNegotiator($allowed_types) {
    $this->allowed_types = array();
    $this->setAllowedTypes($allowed_types);
  }

  /**
   * Set the allowed association types, checking to make sure each
   * combination is valid.
   *
   * @access private
   */
  function setAllowedTypes($allowed_types) {
    foreach ($allowed_types as $pair) {
      list($assoc_type, $session_type) = $pair;
      if (! Auth_OpenID_checkSessionType($assoc_type, $session_type)) {
        return false;
      }
    }
    
    $this->allowed_types = $allowed_types;
    return true;
  }

  /**
   * Add an association type and session type to the allowed types
   * list. The assocation/session pairs are tried in the order that
   * they are added.
   *
   * @access private
   */
  function addAllowedType($assoc_type, $session_type = null) {
    if ($this->allowed_types === null) {
      $this->allowed_types = array();
    }
    
    if ($session_type === null) {
      $available = Auth_OpenID_getSessionTypes($assoc_type);
      
      if (! $available) {
        return false;
      }
      
      foreach ($available as $session_type) {
        $this->addAllowedType($assoc_type, $session_type);
      }
    } else {
      if (Auth_OpenID_checkSessionType($assoc_type, $session_type)) {
        $this->allowed_types[] = array($assoc_type, $session_type);
      } else {
        return false;
      }
    }
    
    return true;
  }

  // Is this combination of association type and session type allowed?
  function isAllowed($assoc_type, $session_type) {
    $assoc_good = in_array(array($assoc_type, $session_type), $this->allowed_types);
    
    $matches = in_array($session_type, Auth_OpenID_getSessionTypes($assoc_type));
    
    return ($assoc_good && $matches);
  }

  /**
   * Get a pair of assocation type and session type that are
   * supported.
   */
  function getAllowedType() {
    if (! $this->allowed_types) {
      return array(null, null);
    }
    
    return $this->allowed_types[0];
  }
}
